1. Field of the Invention
This invention relates generally to a system and method for determining that the state of charge (SOC) of a vehicle battery may be too low to start the vehicle at the next vehicle start-up and, more particularly, to a system and method for determining that the state of charge of a vehicle battery may be too low to start the vehicle at the next start-up, where information concerning the vehicle battery is stored and processed at a remote back-office and transmitted to the vehicle telematically.
2. Discussion of the Related Art
Vehicles typically employ a battery that provides power to various vehicle systems generally when the vehicle engine is not running. The vehicle battery also provides the power necessary to start the vehicle in response to a start command from a vehicle driver, such as turning the ignition key. When the vehicle engine is running, a vehicle generator recharges the vehicle battery. If the battery state of charge (SOC) is too low, the battery may not be able to supply the necessary power to start the vehicle. Further, a low battery SOC impacts the battery state of health (SOH) in the long term, typically resulting in prematurely defective batteries.
A battery's state of charge deteriorates as a result of various reasons. Without any load, a battery has a constant self-discharge that increases as the battery temperature increases. Further, vehicle parasitic loads as a result of the operation of electrical devices when the vehicle is off, such as the periodic wake-up of remote keyless entry systems and security system modules, draws power from the battery and reduces its SOC. Also, vehicle system faults, such as stuck-closed relays, may create inadvertent loads that drain the battery. After market consumer electronic devices, such as CD players, computers and cell phone chargers, plugged in when the vehicle is off will further drain the vehicle battery.
Moreover, depending on driving profile, such as driving frequency, duration and average speed of trips, the battery may not be charged enough by the vehicle generator. Unless the battery is put on an external battery charger, the vehicle battery is only charged by the vehicle generator when the vehicle is driven, which is constrained by vehicle speed. Local trips at low vehicle speed may not allow the generator to charge the battery after supplying power to all of the on-board electrical loads. Infrequent short trips may not charge the battery long enough to recover the charge lost due to the reasons discussed above.
In addition, a battery defect may prevent the battery from suitably accepting or holding charge. Further, the battery's ability to provide a sufficient vehicle start is reduced when its temperature is low, such as below zero Celsius.
Therefore, a system and method are needed to determine the battery state of charge and warn a vehicle driver about a possible vehicle no-start condition.